This invention relates to a process for production of fine powdery metal. More particularly, it relates to a process for production of fine powdery metallic materials of a high purity such as single-metal particles, particles of solid solution-type alloys, alloy particles the surfaces of which have been coated with another metal, and metal particles having plastic coating thereon.
As a metallurgical method for obtaining fine powdery metal, reduction metallurgy has hitherto been known. This method comprises reducing metallic materials existing in the form of oxides, chlorides, fluorides and the like with a reducing agent such as magnesium and calcium to obtain solid metal powder. This method is typically represented by a process for production of beryllium powder by reducing beryllium fluoride with magnesium and a process for production of vanadium powder by reducing vanadium oxide with calcium. This method, however, is applicable to only the production of metals having a high melting point and also cannot be applied to the production of alloys. Furthermore, there are other problems such as an upper limit to the purity of the fine powdery metal obtained and the tendency of the particle size to become ununiform.
In addition to the above mentioned method, a spray method has been known as a method for obtaining fine powdery metals such as zinc. This method comprises dividing molten metal finely by spraying it with a pressurized gas to obtain metal powder. This method only divides molten metal finely and cannot control the composition of the metal. Moreover, in accordance with this method, the shapes of the resulting fine particles are not uniform, the particle size is not constant, and the fineness thereof is limited to an order of several tens of microns.
Furthermore, methods utilizing laser induced chemical reaction, metal evaporation in low pressure inert gas and supersonic condensation, are known to produce fine powdery metals.